Anthony Beevor at the Guardian Hay festival. Photograph: Martin Argles for the Guardian

Journalism is the enemy of history when it comes to constructing a scholarly account of recent conflicts, according to Britain's leading military historian.

Speaking at the Guardian Hay festival, Antony Beevor said that the tendency since the Falklands and the first Iraq war had been for journalists to attempt "an instant history – what I call history on the hoof". In many cases this had "spoilt the ground for the future historian", said the author of D-Day and Stalingrad.

He said he was "not blaming the journalists" but argued that they were caught up in the "acceleration of history, and I am not sure that's right. Journalism is an instant account and history must be a reflective account."

He called increased freedom of information – a valuable tool for journalists – a "double-edged sword" for the historian. "Now, with journalists wanting to write history on the hoof there is a tremendous pressure on people wanting to protect themselves and their reputations for the future; and they are weeding out information before it gets to the archive, or wiping the digital stuff, and I don't think historians are going to be able to get at material in the same way in the future."

He added: "Some things do need to remain secret and the more things are opened up immediately the more will be wiped early on. It's a natural human reaction that people in positions of responsibility will want to clean up any embarrassments or difficulties, and with email and all the rest of it, it is easier to do so."

For these reasons, he said, he "would not touch Iraq with a bargepole". Asked if a reliable history of Iraq were possible, he said: "I don't think it is … in fact if my publishers asked me to do it I would definitely stick my head firmly in the sand."

Beevor also threw himself into the debate on the history curriculum, after education secretary Michael Gove enthusiastically embraced Niall Ferguson's campaign for "real history" at the Guardian Hay festival.

Children should be taught narrative history, said Beevor. "History is a question of cause and effect. You need to take events in order to make sense of them."

Asked whether local history might be incorporated into this grand-sweep approach he said: "How far you go into the local weaving industry or iron industry – I'm sorry, I think that tends to be tourist history rather than real history."

The importance for students was not just the facts but analysing them and producing clear arguments in the form of an essay. "This is the danger, the thing we tended to have lost. The essay is vital," he said. It was wrong to reduce history to multiple-choice questions "as if they are playing Who Wants to be a Millionaire".

Unlike other subjects, history produced employable skills, he said. "Media studies is seen as a bad joke as far as employers are concerned ... The 'soft' subjects make me rather angry because it is a betrayal of the students. They think they are getting a real qualification and in fact they have been conned."

Turning to his books Stalingrad and Berlin, the historian said it would be impossible to write them now, since the Soviet archives on which they rely for detailed information have closed. "I happened to be incredibly lucky in timing. Towards the end of Yeltsin's presidency he appointed a minister of archives who forced the military to open their archives; this had never happened before. This was 1995, when I was starting on Stalingrad." Later, he said, the FSB, the Russian security service, began to track all files accessed by foreign historians. Eventually the archives closed altogether.

A further problem was the fragility of the poor-quality, wartime paper. "It is crumbling," he said. "There's a pile of brown dust as you turn over each page. It is worrying. They haven't got the resources to transfer them to microfilm and microfiche."